1. Carbon Dioxide Emissions
Carbon dioxide (CO2) is a well-known greenhouse gas and attempts to reduce the emissions of this gas into the atmosphere are desirable. CO2 is commonly formed when hydrocarbon-based materials are processed. As an example, a gas-to-liquids (GTL) process converts roughly two-thirds of the starting gas (methane or natural gas) into hydrocarbon-based liquid products, with the other one-third being emitted as CO2. See, e.g., Sousa-Aguiar et al., “Natural Gas Transformations: The Path to Refining in the Future,” Catalysis Today, vol. 101, pp. 3-7, 2005. The current high costs associated with capturing and/or utilizing this CO2 using conventional amine scrubbing technology coupled with sequestration of high pressure CO2 are such that doing so is generally not economically-viable.
2. Biofuels
A common route to making transportation fuels is to convert vegetable oils to biodiesel via transesterification of the triglyceride species contained therein, so as to yield fatty acid methyl esters. See, e.g., Huber et al., “Synthesis of Transportation Fuels from Biomass: Chemistry, Catalysts, and Engineering,” Chem. Rev., vol. 106, pp. 4044-4098, 2006; and Antolín et al., “Optimisation of Biodiesel Production by Sunflower Oil Transesterification,” Bioresource Technology, vol. 83, pp. 111-114, 2002. However, a major drawback of this type of biodiesel is that the fatty acid methyl esters (FAME) generally have poor oxidation stability and poor low temperature performance (i.e., high cloud and pour points). One way around this is to hydroprocess the vegetable oil to separate the fatty acid-derived paraffins from the species comprising oxygen-containing functional groups, and to then isomerize the isolated paraffins via an isomerization process (see, e.g., Zones et al., U.S. Pat. No. 5,300,210) to produce a low pour point diesel. Such a process, however, still has the drawback that production is limited by the supply of vegetable oil-which in many cases leads to a competition of fuel versus food. See Ragauskas et al., “The Path Forward for Biofuels and Biomaterials,” Science, vol. 311, pp. 484-489, 2006.
Reducing CO2 emissions via routes other than sequestration are also challenging. The exceptional thermodynamic stability of this molecule makes its chemical conversion likewise quite costly. Accordingly, a cost-effective way (method) of mitigating CO2 emissions in GTL processing would be a welcome development, particularly wherein such a method could be further used to support the production of high-quality biofuels with a feedstock that does not compete directly with food.